A plug and a socket that are attached to a container for storing a liquid, such as a chemical solution, which is used for semiconductor production, are conventionally known (for example, see Japanese Unexamined Patent Application, Publication No. 2009-173326).
The plug disclosed in Japanese Unexamined Patent Application, Publication No. 2009-173326 is press-fit into an opening of the liquid storing container and thus is attached to the opening of the liquid storing container. The socket disclosed in Japanese Unexamined Patent Application, Publication No. 2009-173326 includes a sleeve having an inside screw formed therein. The inside screw of the sleeve is fastened to an outside screw, which is formed on the outside of the opening of the liquid storing container, to thereby attach the socket to the outside of the opening of the liquid storing container.